From about day __1__, histotrophe accumulates opposite the openings of the uterine glands. These accumulations, known as __2__, are visible as small, white, round vesicles that cause shallow, focal invaginations of the chorion (see Fig. 34). From the __2__, histotrophe spreads radially between chorionic and uterine epithelium and is taken up by the chorionic epithelium. Chorionic villi also grow into the __2__ to facilitate the absorption of histotrophe. The __2__ increase in number as the gestation progresses.